A motor vehicle typically includes a fuel vapor control apparatus which exposes a vapor dome in a fuel tank of the vehicle to the atmosphere without releasing fuel vapor. The fuel vapor control apparatus commonly includes a vapor storage canister, a vent valve exposed to a vapor dome above a pool of liquid fuel in the fuel tank, and a vapor duct between the vent valve and the storage canister. A mixture of air and fuel vapor migrates from the vapor dome to the storage canister where an adsorbent, e.g. carbon granules, strips the fuel vapor from the mixture so that only uncontaminated air exhausts from the canister to the atmosphere. The fuel vapor is retained on the adsorbent until the canister is later purged by combustion air. In order to maintain exposure of the vapor dome to the atmosphere when the motor vehicle is parked on an incline, e.g. on a parking deck ramp or on a hill, it is known to mount a plurality of vent valves on the top of the fuel tank at locations which assure that at least one of the vent valves always communicates with the vapor dome even though others may be submerged in liquid fuel. Because the performance of adsorbents degrades when contaminated by liquid fuel, vent valves in fuel vapor control apparatuses are typically constructed to automatically close when submerged in liquid fuel Even when a vent valve is closed, however, there is a risk of leakage of liquid fuel through the vent valve if the motor vehicle remains parked on the incline for an extended period. Accordingly, the industry continues to seek improved fuel vapor control apparatuses which minimize the likelihood of adsorbent contamination by liquid fuel leaking through vent valves submerged in liquid fuel.